Russia’s military laid out what is now seen as a blueprint for cyberwarfare with a 2013 article in a professional journal by Gen. Valery Gerasimov, the chief of Russia’s General Staff. Cyberspace, wrote Gen. Gerasimov, “opens wide asymmetrical possibilities for reducing the fighting potential of the enemy.” At the time, Russia’s military was absorbing the lessons of the Arab Spring, when social media played a key role in mobilizing leaderless protests that upended the political order across North Africa and the Middle East. “In North Africa, we witnessed the use of technologies for influencing state structures and the population with the help of information networks,” the article stated. “It is necessary to perfect activities in the information space, including the defense of our own objects.” Now that doctrine is likely to come under more scrutiny following new U.S. sanct...